(1) Field of the Invention
This invention generally relates to fire resistant and heat insulating compositions and more particularly to compositions capable of withstanding direct exposure to flames and high temperatures.
(2) Description of the Related Art
Various fire resistant and/or heat insulating materials or compositions are known. For example, masonry materials, such as fire brick, are capable of providing a fire or heat barrier, but are of limited usefulness as a fire resistant coating because these materials are generally not available in a pliant, moldable form. Furthermore, masonry materials are heavy and cumbersome to use, as well as costly. Drywall, which is typically comprised of compressed gypsum sandwiched between paperboard panels, is often used as a fire barrier, but its fire resistance properties are dependent upon the thickness of the drywall. Generally, drywall that is at least 5/8" thick is considered "fire resistant drywall." Even though considered "fire resistant", drywall of this thickness will readily burn when directly exposed to flames. Therefore, "fire-resistant" drywall is not considered an effective fire barrier for high temperature applications or applications involving exposure to flames. Furthermore, drywall is not suitable for coating and molding applications.
Another group of fire and heat resistant compositions are those that contain asbestos. Although asbestos-containing compositions are considered effective in providing fire-resistance and heat insulating properties, it has been discovered that exposure to asbestos can result in adverse health consequences and its use has been severely restricted. Various non-asbestos containing fireproofing and insulating compositions have subsequently been developed which have not been altogether adequate for high temperature applications.
One non-asbestos containing fireproofing composition is disclosed in U.S. Pat. No. 4,851,044. The composition disclosed therein consists primarily of a mixture of exfoliated vermiculite, clay, silica, mica, biotite and an organic adhesive. This composition is of limited usefulness in high temperature applications because it cannot withstand exposure to flames. Further, vermiculite is known to burn when directly exposed to flames.
Other problems have been associated with various other fire-resistant or heat insulating compositions such as the release of smoke or noxious fumes when exposed to high temperatures or flames, the breakdown of the material after prolonged exposure to high temperatures, or the unsuitability of a composition for use as a coating onto an article or for molding into a particular shape.
Numerous industrial applications require the use of a fire-resistant material as a coating on various devices or, in the event a fire breaks out, to serve as a fire stop or barrier to confine the fire. A particular need is known to exist in the nuclear power plant industry where it is necessary to protect electrical circuits, machinery, conduit, pipes and the like.
A need exists, therefore, for a non-asbestos containing fire resistant and high temperature insulating composition that overcomes the foregoing problems.